Magnetic resonance imaging (MRI) guided transperineal targeted prostate biopsy has become a valuable instrument for detection of prostate cancer in patients with continuing suspicion for aggressive cancer after transrectal ultrasound guided (TRUS) guided biopsy. The MRI-guided procedures are performed using mechanical targeting devices or templates, which suffer from limitations of spatial sampling resolution and/or manual in-bore adjustments. To overcome these limitations, we developed and clinically deployed an MRI-compatible piezoceramic-motor actuated needle guidance device, Smart Template, which allows automated needle guidance with high targeting resolution for use in a wide closed-bore 3-Tesla MRI scanner. One of the main limitations of the MRI-guided procedure is the lengthy procedure time compared to conventional TRUS-guided procedures. In order to optimize the procedure, we assessed workflow of 30 MRI-guided biopsy procedures using the Smart Template with focus on procedure time. An average of 3.4 (range: 2~6) targets were preprocedurally selected per procedure and 2.2 ± 0.8 biopsies were performed for each target with an average insertion attempt of 1.9 ± 0.7 per biopsy. The average technical preparation time was 14 ± 7 min and the in-MRI patient preparation time was 42 ± 7 min. After 21 ± 7 min of initial imaging, 64 ± 12 min of biopsy was performed yielding an average of 10 ± 2 min per tissue sample. The total procedure time occupying the MRI suite was 138 ± 16 min. No noticeable tendency in the length of any time segment was observed over the 30 clinical cases.

Intra-operative medical imaging enables incorporation of human experience and intelligence in a controlled, closed-loop fashion. Magnetic resonance imaging (MRI) is an ideal modality for surgical guidance of diagnostic and therapeutic procedures, with its ability to perform high resolution, real-time, high soft tissue contrast imaging without ionizing radiation. However, for most current image-guided approaches only static pre-operative images are accessible for guidance, which are unable to provide updated information during a surgical procedure. The high magnetic field, electrical interference, and limited access of closed-bore MRI render great challenges to developing robotic systems that can perform inside a diagnostic high-field MRI while obtaining interactively updated MR images. To overcome these limitations, we are developing a piezoelectrically actuated robotic assistant for actuated percutaneous prostate interventions under real-time MRI guidance. Utilizing a modular design, the system enables coherent and straight forward workflow for various percutaneous interventions, including prostate biopsy sampling and brachytherapy seed placement, using various needle driver configurations. The unified workflow compromises: 1) system hardware and software initialization, 2) fiducial frame registration, 3) target selection and motion planning, 4) moving to the target and performing the intervention (e.g. taking a biopsy sample) under live imaging, and 5) visualization and verification. Phantom experiments of prostate biopsy and brachytherapy were executed under MRI-guidance to evaluate the feasibility of the workflow. The robot successfully performed fully actuated biopsy sampling and delivery of simulated brachytherapy seeds under live MR imaging, as well as precise delivery of a prostate brachytherapy seed distribution with an RMS accuracy of 0.98mm.

Magnetic resonance imaging (MRI) provides high resolution multi-parametric imaging, large soft tissue contrast,
and interactive image updates making it an ideal modality for diagnosing prostate cancer and guiding surgical
tools. Despite a substantial armamentarium of apparatuses and systems has been developed to assist surgical
diagnosis and therapy for MRI-guided procedures over last decade, the unified method to develop high fidelity
robotic systems in terms of accuracy, dynamic performance, size, robustness and modularity, to work inside
close-bore MRI scanner still remains a challenge. In this work, we develop and evaluate an integrated modular
hardware and software system to support the surgical workflow of intra-operative MRI, with percutaneous
prostate intervention as an illustrative case. Specifically, the distinct apparatuses and methods include: 1) a
robot controller system for precision closed loop control of piezoelectric motors, 2) a robot control interface
software that connects the 3D Slicer navigation software and the robot controller to exchange robot commands
and coordinates using the OpenIGTLink open network communication protocol, and 3) MRI scan plane alignment
to the planned path and imaging of the needle as it is inserted into the target location. A preliminary experiment
with ex-vivo phantom validates the system workflow, MRI-compatibility and shows that the robotic system has
a better than 0.01mm positioning accuracy.

Image guided prostate interventions have been accelerated by Magnetic Resonance Imaging (MRI) and robotic
technologies in the past few years. However, transrectal ultrasound (TRUS) guided procedure still remains as vast
majority in clinical practice due to engineering and clinical complexity of the MRI-guided robotic interventions.
Subsequently, great advantages and increasing availability of MRI have not been utilized at its maximum capacity in
clinic. To benefit patients from the advantages of MRI, we developed an MRI-compatible motorized needle guide device
"Smart Template" that resembles a conventional prostate template to perform MRI-guided prostate interventions with
minimal changes in the clinical procedure. The requirements and specifications of the Smart Template were identified
from our latest MRI-guided intervention system that has been clinically used in manual mode for prostate biopsy. Smart
Template consists of vertical and horizontal crossbars that are driven by two ultrasonic motors via timing-belt and mitergear
transmissions. Navigation software that controls the crossbar position to provide needle insertion positions was also
developed. The software can be operated independently or interactively with an open-source navigation software, 3D
Slicer, that has been developed for prostate intervention. As preliminary evaluation, MRI distortion and SNR test were
conducted. Significant MRI distortion was found close to the threaded brass alloy components of the template. However,
the affected volume was limited outside the clinical region of interest. SNR values over routine MRI scan sequences for
prostate biopsy indicated insignificant image degradation during the presence of the robotic system and actuation of the
ultrasonic motors.

Automatic tracking and scan plane control in MRI-guided therapy is an active area of research. However, there has been
little research on tracking needles without the use of external markers. Current methods also do not account for possible
needle bending, because the tip does not get tracked explicitly. In this paper, we present a preliminary method to track a
biopsy needle in real-time MR images based on its visible susceptibility artifact and automatically adjust the next scan
plane in a closed loop to keep the needle's tip in the field of view. The images were acquired with a Single Shot Fast Spin
Echo (SSFSE) sequence combined with a reduced field of view (rFOV) technique using 2D RF pulses, which allows a
reduction in scan time without compromising spatial resolution. The needle tracking software was implemented as a
plug-in module for open-source medical image visualization software 3D Slicer to display the current scan plane with the
highlighted needle. Tests using a gel phantom and an ex vivo tissue sample are reported and evaluated in respect to
performance and accuracy. The results proved that the method allows an image update rate of one frame per second with
a root mean squared error within 4 mm. The proposed method may therefore be feasible in MRI-guided targeted therapy,
such as prostate biopsies.

One of the key technical challenges in developing an
extensible image-guided navigation system is that of interfacing with external proprietary hardware. The technical challenges arise from the constraints placed on the navigation system's hardware and software. Extending a navigation system's functionality by interfacing with an external hardware device may require modifications to internal hardware components. In some cases, it would
also require porting the complete code to a different operating system that is compatible with the manufacturer supplied application programming interface libraries and drivers. In this paper we describe our experience extending a multi-platform navigation system, implemented using the image-guided surgery toolkit IGSTK, to
support real-time acquisition of 2-D ultrasound (US) images acquired with the Terason portable US system. We describe the required hardware and software modifications imposed by the proposed extension and how the OpenIGTLink network communication protocol enabled us to minimize the changes to the system's hardware and software. The resulting navigation system retains its platform independence with the added capability for real-time image acquisition independent of the image source.

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